Add Thanos monitoring

Summary

Adapt some essential rules for Thanos components monitoring

e.g. https://github.com/thanos-io/thanos/blob/main/examples/alerts/alerts.md & https://thanos.io/v0.35/components/rule.md/#must-have-essential- ruler-alerts

Add Grafana dashboards for Thanos components

https://github.com/thanos-io/thanos/tree/main/examples/dashboards